The invention relates to separation of fluids, and more particularly to SiOC membranes and methods of making the same.
Polymer derived ceramics (PDCs) membranes possess excellent thermal and chemical stability and can be used under critical process conditions where most of the polymeric membranes are unstable. PDCs have mainly two families: one is made of silicon, oxygen and carbon, commonly known as silicon oxycarbide (SiOC); while the other one is made of silicon, carbon and nitrogen, known as silicon carbonitride. Varieties of PDCs with multifunctional properties have evolved from these two families by adding different dopants. The composition of PDCs is non-stoichiometric, in general, and that determines their structure.
PDCs are obtained from the pyrolysis of polymer precursor. There exists strong bonding between silicon and carbon in the polymer that prevents carbon from volatilizing as a hydrocarbon during pyrolysis. The polymer pyrolysis process is a low-temperature route for making high-temperature ceramics as the pyrolysis is completed below about 1200° C. In recent years, ternary PDC systems made from SiCN and SiCO have attracted interest because of their unusual properties, such as the absence of steady state creep, presence of visco-elasticity at very high temperatures, oxidation resistance, corrosion resistance and optical properties.
Due to these properties PDCs are a suitable candidate for forming membranes. However, in many applications a major concern in the processing of membranes is to achieve nanopores with narrow pore size distribution. Apart from narrow pore size distribution, membranes need to have chemical and mechanical stability for efficient separation process. For example, lack of porous membranes with uniform pore size distribution makes the separation of bio-molecules like viruses and proteins relatively difficult.
Therefore, it would be desirable to provide membranes, which have the desired pore size distribution and that exhibit chemical and mechanical stability.